Conventionally, turret punch presses are generally used as a punching machine that is able to singly produce blanks of a plurality of certain shapes. A turret punch press comprises a pair of upper and lower turrets which hold punches and dies respectively and punches a workpiece with the punch and die which have been set in positions under a hammer by indexing. The turret punch presses can deal with a comparatively small number of lots, say, 100 to 5,000 lots so that they have met so far the needs of their market as a machine tool suited for use in the small quantity production of multiple kinds of items.
In recent years, however, there have arisen strong demands in the market towards the sales of multiple items in a much smaller number of lots with short delivery times. Under such a situation, the conventional turret punch presses, which can hold up to about 70 tool sets only, can no longer meet the market demands.
To overcome this problem, one turret punch press provided with an automatic tool set replacement system has been proposed and put to practical use. According to this punching machine, a tool set storage (i.e., tool set repository) for storing a number of tool sets is incorporated in or installed separately from the turret punch press and the automatic tool set replacement system supplies tool sets to the punching head from the tool set storage.
Japanese Patent Publication No. 4-11283 (1992) discloses one example of punch presses provided with an automatic tool set replacement system. According to this publication, a magazine for storing tool sets is disposed, in the form of an arc, in the area around the center of rotation of a tool mounting/dismounting apparatus. Japanese Patent Publication Laid-Open No. 4-13424 (1992) discloses another example in which a tool set storage is disposed within a gate-like frame and a tool set replacement system is provided so as to reciprocate freely between the tool set storage and the turret. A further example is disclosed in Japanese Patent Publication Laid-Open No. 61-115630 (1986) in which a tool set magazine is so supported as to be rotatable about a horizontal, geometric axis and tool set replacement is performed by the linear, replacing motion of a tool set replacement system.
All of the prior punch presses with an automatic tool set replacement system disclosed in the above publications however fail in remarkably increasing the capacity of the tool set magazines to accommodate a large number of tool sets. In addition, the magazines of these punch presses require an extremely large space for installation if a number of tool sets are accommodated in them, which increases the distance between the punching head and the tool set storage position (i.e., the distance for tool set delivery), resulting in an increase in the time required for tool set replacement. As described above, in the prior turret punch presses equipped with an automatic tool set replacement system, if emphasis is placed on tool set replacement speed, it becomes difficult to increase the number of tool sets to be stored, and on the other hand, if emphasis is placed on the number of tool sets to be stored, tool set replacement speed decreases.
In the case of a punch press with an automatic tool set replacement system, a so-called tool set replacement operation is necessary, in which a tool set with which punching operation has been done is removed from the punching head while another tool set to be used for the next punching operation is mounted on the punching head.
One conventional example of tool set replacement systems for automatically performing such a tool set replacement operation is disclosed in Japanese Patent Publication No. 54-6751 (1979). According to the publication, a holder which is equipped with a holding mechanism for holding a tool set is inserted, in a horizontal direction, into the tool set mounting section of the punching press and while the tool set is locked by a locking device within the tool set mounting section, the holding mechanism is disengaged from the holder so that only the holder can be removed from the punch press in a horizontal direction. Japanese Patent Publication No. 4-13425 (1992) discloses another tool set replacement system which is horizontally movable to mount or dismount a tool set for replacement, and this tool set replacement system is equipped with a disengagement system for disengaging the system from the turret.
The tool set replacement system disclosed in the publication No. 54-6751 suffers from the following problem. Since a tool set is inserted only by a reciprocating motion, the gap between the tool set and the ram receiving section can be made small provided that the operator carefully inserts the tool set and makes certain by touching the tool set. However, when automatic replacement is performed, a somewhat generous gap should be kept between them, which inevitably causes backlash after mounting the tool set. Further, this system is designed to hold a tool set only by the resilient deformation of tool set holding arms and therefore positioning of the holder cannot be performed at a high speed. The tool set replacement system disclosed in the publication No. 4-13425 as mentioned above is also constructed so as to insert a tool set only by horizontal motion, so that an occurrence of backlash cannot be avoided. Another disadvantage of this system is that holders should be installed as many as tool sets.
In consideration of the foregoing problems, the invention aims to provide a compact-sized punch press which can store a large number of tool sets to cope with the small quantity production of multiple kinds of items and which ensures a tool set replacement speed as high as that of the conventional turret punch presses.
Another object of the invention is to provide a tool set mounting method by which high-speed tool set replacement can be performed without positioning the tool set delivery means with high accuracy and which prevents the tool set from contacting the tool set mounting section during insertion to eliminate the occurrence of an unpleasant sound caused by the contact between the tool set and the tool set mounting section.